In applications such as electronic notice boards, it is frequently required to update the information displayed. The updating can be done by transmissions through landlines from a central station, which has the disadvantage that the electronic notice board cannot be readily moved around. Alternatively, the user equipment may incorporate a dedicated radio receiver which is hard wired into the electronic notice board and any updating is done by way of a radio transmission. Such an equipment is disclosed in British Patent Specification GB 2 247 332 A. Building a radio receiver into the electronic notice board or other end user equipment has a number of drawbacks, in that 1) the positioning of the equipment has to be a compromise between viewability and the best possible reception of radio signals, and 2) any equipment containing a radio receiver has to be submitted for type approval by the Radio Regulatory Authorities. Individual type approval is necessary because, amongst other things, an electrically conductive link between the radio receiver and the end user equipment may affect the radio frequency (r.f.) properties of the radio receiver. The consequence of this is that a manufacturer of equipment will be reluctant to have too many models because of the time and cost of obtaining type approval.